Fixing arrangement

ABSTRACT

A fixing arrangement for holding a cutting tooth on a cutter. The cutting tooth has a tool head and a shank. The shank is accommodated in a shank-receiving element of the cutter or a holder connected to the cutter. One or several bearing surfaces of the cutting tooth each lies on support surfaces of the cutter. The cutting tooth can be supported in a stable and reliable manner by inclining the support surfaces and the bearing surfaces in a peripheral direction and by providing the cutter with a shoulder which is arranged in the direction of the cutter in an offset position relative to the bearing surfaces, the shoulder being associated with the cutting tooth at a distance.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a securing arrangement for retaining a cutting tooth on a drill bit, wherein the cutting tooth has a tool head and a shaft, the shaft is accommodated in a shaft receiver of the drill bit or of a holder which is connected to the drill bit, and the cutting tooth rests on support faces of the drill bit with one or a plurality of contact faces.

2. Discussion of Related Art

A securing arrangement is known from European Patent Reference EP 0 439 821 A 1. In this case, the drill bit includes pocket-shaped notches, into which each base part is welded. The base part has a shaft receiver, which is tapered. The shaft of the cutting tooth can be inserted into the shaft receiver. To create a cone connection, the shaft has a conical outer outline. A spring cotter is used to secure the cone connection and connects the base part to the shaft.

In operation, particularly where the loads are jerky and intermittent, the cone connection can become worn. The cutting tooth is then no longer retained without play and this leads to a heavy increase in wear until the tool finally breaks.

SUMMARY OF THE INVENTION

It is one object of this invention to provide a securing arrangement of the type mentioned above but where the cutting tooth is retained on the drill bit in a secure manner.

This object is achieved with support faces and contact faces that are set to be inclined in a circumferential direction. The drill bit includes a shoulder which is offset relative to the contact faces in the direction of the axis of the drill bit and is associated with and spaced from the cutting tooth. The cutting forces occurring during the cutting operation can be absorbed mostly via the inclined support faces. This type of supporting, in interaction with the space, makes it possible for the shaft of the cutting tooth to be substantially free of the cutting forces and reduces the danger of the tool breaking. Also, the space also makes it possible for the cutting tooth to be adjusted if the support face of the drill bit and/or the contact face of the cutting tooth becoming worn.

According to a preferred embodiment of this invention, the shaft receiver is admitted partially into the shoulder face, which is formed by the shoulder and faces the cutting tooth. A particularly sturdy support of the cutting tooth is produced when the drill bit provides two contact faces for each cutting tooth, and the two contact faces are set opposite one another. When the securing arrangement is developed so that the cutting tooth includes a threaded portion, which is mounted on the shaft, a nut is screw-connectable to the threaded portion, and the cutting tooth is pressed onto the support faces via the contact faces in a pre-tensioned manner by the nut, so that the shaft can then build up an initial tensioning, which absorbs even intermittent, jerky tool loads in a secure manner without loosening of the threaded connection.

The securing arrangement is configured advantageously so that, at least over a portion of its longitudinal region, which extends in the direction of the axis of the drill bit, the shaft of the cutting tooth is surrounded around the circumference completely by the shaft receiver. At the same time, a lateral deviation of the cutting tooth is prevented in a secure manner. In this case, the shaft of the cutting tooth includes at least one calibrating receiver, which is set back relative to the inner wall of the shaft receiver. In this case, the cutting tooth can then be produced true to measurement in the region of its shaft. Superfluous material can be used in the region of the calibrating receiver.

In one embodiment of this invention, the shaft of the cutting tooth is tapered at least over a portion of its longitudinal extension in the direction of its free end. The shaft receiver is also tapered at least in a regional manner, and an outside cross-section of the shaft is smaller than the inside cross-section of the shaft receiver. This arrangement simplifies the mounting of the cutting tooth into the shaft receiver. If the tool head of the cutting tooth includes one or a plurality of radial recesses in its region directed radially inwards, then material pockets are formed on the cutting tooth. Residue material collects in the pockets and forms a layer for protection against wear.

An improved cutting performance is provided if the tool head is closed at its circumferential end region with triangular, convexly curved shaped faces. In addition, the hard material elements are admitted into a web, which is disposed in a region of the cutting tooth lying radially outwards and which extends in the direction of the axis of the drill bit and protrudes above a base part of the cutting tooth. The hard material elements protrude in a regional manner in the radial direction above the web. The hard material elements form calibrating pins, which constantly free-cut the cutting tooth in the drill hole.

To improve the cutting performance even further, at a region remote from the shaft, the tool head of the cutting tooth includes a top face, into which a hard material insert, such as a hard metal insert, is inserted.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention is described in detail in view of an embodiment represented in the drawings, wherein:

FIG. 1 is a side view of a drill bit;

FIG. 2 is a perspective view of the drill bit in FIG. 1;

FIG. 3 is a vertical section view of the drill bit;

FIG. 4 is a detailed representation taken from the view shown in FIG. 3;

FIG. 5 is a side perspective view of a cutting tooth;

FIG. 6 is a rear perspective view of the cutting tooth shown in FIG. 5; and

FIG. 7 is a section view taken through the shaft of the cutting tooth as shown in FIGS. 5 and 6.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1 and 2 show a drill bit 10, produced in one piece from a casting that is annular and has a base body 11. On a lower edge, the base body 11 has a securing ring 19, which is in the form of a mounting. On a side remote from the securing ring 19, mounting projections 21 are integrally formed around the circumference on the base body 11. The mounting projections 21, in this case, are spaced equally from one another so that a space 16 is produced. The base body 11 has webs 15 between the mounting projections 21. The webs 15 each form an end face, which extends in the radial direction. All end faces of the webs 15 rest on a common plane. Inclined faces 18 proceed from the end faces at angle. The inclined faces 18, in this case, are facing the interior, which is surrounded by the drill bit 10. The end faces and the inclined faces 18 pass over at their circumferential ends into deflecting faces 26 of the mounting projections 21. The deflecting faces 26 project above the end faces in the direction of the axis of the drill bit. The deflecting faces 26 each pass over into a roof portion 25 that passes over into a support face 24. The support face 24, in this case, is disposed at an angle to the horizontal. The two support faces 24 of one mounting projection 21, in this case, are aligned opposite one another and are part of a tool receiver 20. The tool receiver 20 has a shaft receiver 22, which has an oval cross-section, with an insertion channel 22.1 between the two support faces 24. The insertion channel 22.1 ends in an opening 12 and is machined into the base body 11 in the shape of a window. The opening 12, in this case, is developed so that it widens outwardly in a continuous manner proceeding from the inner wall 17.1 of the base body 11.

The disposition and development of the insertion channel 22.1 and of the opening 12 is shown in FIGS. 2 and 4. As shown in FIG. 2, cutting teeth 30 can be inserted into the tool receiver 20. The development of the cutting teeth 30 is shown in FIGS. 5 to 7. According to these Figures, the cutting teeth 30 have a tool head 31, on which a shaft is integrally formed. The tool head 31 has hard metal inserts 35. At its free end the shaft 32 has a threaded portion 33.

The cutting tooth 30 is inserted with its shaft 32 into the insertion channel 22.1. In the installed state, the cutting tooth 30 rests with corresponding mating faces on the support faces 24.

The threaded portion 33 extends into the region of the opening 12, so that a nut 34 can be screw-connected. The cutting tooth 30 can be tensioned on the support faces 24 with the nut 34. As the cross-sectional geometry of the shaft 32 of the cutting tooth 30 is adapted to the outline of the insertion channel 22.1, it is retained in a non-rotatable manner. As shown in FIG. 1, the cutting tooth 30 has two shaped faces 36, which pass over into the deflecting faces 26 of the support parts 25 in a seamless manner.

To calibrate the drill bit 10, projections 13 are disposed on the outer face of the base body 11 and have elements 14 produced from hard metal for protection against wear.

In the region of the inner wall 17.1, the base body 11 also has projections 17.2 which extend into the interior of the drill bit 10 and optimize protection against wear at that location.

FIGS. 5 to 7 provide a more detailed representation of one embodiment of a cutting tooth 30. The cutting tooth 30 has a tool head 31, on which a shaft 32 is integrally formed via a rounding transition. The shaft 32 ends at the end remote from the tool head 31, in a threaded portion 33. The tool head 31 has an upper top face 31.1, into which a hard metal insert 35 is admitted. To form a receiver for the hard metal insert, which is in the form of a straight pin, a web 37.1, 37.2 proceeds from the top face 31.1 at both the front and the rear.

As shown in FIG. 5, the top face 31.1, near or in the region of the inside of the cutting tooth 30, passes over into a steeply descending concavely curved wall 38.2 which is divided longitudinally by two ribs 38 and the web 37.1. The ribs 38 and the web 37.1 form recesses 38.1, which serve as material pockets for accommodating residue material. As shown in FIG. 6, at the rear the top face passes over into a wall 38.3, which extends parallel to the axis of rotation of the drill bit 10. The wall 38.3 supports the web 37.2. The web 37.2 has hard material elements 39.3 that protrude above the web 37.2. The walls 38.2 and 38.3 pass over into one another at the sides of the cutting tooth 30 by shaped faces 36 that are triangular and are convexly curved.

The shaft 32 is adjacent to a base part 39 of the tool head 31. The shaft 32 has an oval cross-section, as shown in FIG. 7. The shaft 32 forms calibrating receiver 31.1 on the two longitudinal sides. Flat regions 32.2 are provided at the side of the shaft 32 and serve the calibration. Consequently, four true to measurement shaft regions can be forged between the calibrating receiver 31.1 and the flat regions 32.2. The shaft regions prevent the shaft 32 from jamming when inserted into the shaft receiver 22. 

1. A securing arrangement for retaining a cutting tooth (30) on a drill bit (10), wherein the cutting tooth (30) includes a tool head (31) and a shaft (32), the shaft (32) is accommodated in a shaft receiver (22) of one of the drill bit (10) and a holder connected to the drill bit (10), and the cutting tooth (30) rests on support faces (24) of the drill bit (10) with at least one contact face (39.1), the securing arrangement comprising: the support faces (24) and the contact faces (39.1) inclined in a circumferential direction, the drill bit (10) having a shoulder (27) offset relative to the at least one contact face (39.1) in a direction of an axis of the drill bit (10) and associated with and spaced from the cutting tooth (30).
 2. The securing arrangement according to claim 1, wherein the shaft receiver (22) is admitted at least partially into a shoulder face formed by the shoulder (27) and faces the cutting tooth (30).
 3. The securing arrangement according to claim 2, wherein the drill bit (10) has two of the contact faces (39.1) for each cutting tooth (30), and the two contact faces (39.1) are opposite one another.
 4. The securing arrangement according to claim 3, wherein the cutting tooth (30) has a threaded portion (33), mounted on the shaft (32), a nut (34) is screw-connectable to the threaded portion (33), and the cutting tooth (30) is pressed onto the support faces (24) via the contact faces (39.1) in a pre-tensioned manner by the nut (34).
 5. The securing arrangement according to claim 4, wherein at least over a portion of a longitudinal region extending in the direction of the axis of the drill bit, the shaft (32) of the cutting tooth (30) is circumferentially surrounded by the shaft receiver (22).
 6. The securing arrangement according to claim 5, wherein the shaft (32) of the cutting tooth (30) includes at least one calibrating receiver (32.1) setback relative to an inner wall of the shaft receiver (22).
 7. The securing arrangement according to claim 6, wherein that the shaft (32) of the cutting tooth (30) is tapered at least over a portion of a longitudinal extension in a direction towards a free end and the shaft receiver (22) is tapered at least in a regional manner, and an outside cross-section of the shaft (32) is smaller than an inside cross-section of the shaft receiver (22).
 8. The securing arrangement according to claim 7, wherein the tool head (31) of the cutting tooth (30) includes at least one radial (38.1) near a region directed radially inwards.
 9. The securing arrangement according to claim 8, wherein the tool head (31) is closed at circumferential end regions with triangular convexly curved shaped faces (36).
 10. The securing arrangement according to claim 9, wherein the tool head (31) has at least one element (39.3) of hard material near a second region directed radially outwards.
 11. The securing arrangement according to claim 10, the at least one hard material element (39.3) is admitted into a web (37.2), disposed near the cutting tooth (30) lying radially outwards and extending in the direction of the axis of the drill bit and protruding above a base part (39) of the cutting tooth (30), and the hard material elements (39.3) protrude in a regional manner radially above the web (39.2).
 12. The securing arrangement according to claim 11, wherein remote from the shaft (32) the tool head (31) of the cutting tooth (30) has a top face (31.1) into which a hard material insert is inserted.
 13. The securing arrangement according to claim 1, wherein the drill bit (10) has two of the contact faces (39.1) for each cutting tooth (30), and the two contact faces (39.1) are opposite one another.
 14. The securing according to claim 1, wherein the cutting tooth (30) has a threaded portion (33) mounted on the shaft (32), a nut (34) is screw-connectable to the threaded portion (33), and the cutting tooth (30) is pressed onto the support faces (24) via the contact faces (39.1) in a pre-tensioned manner by the nut (34).
 15. The securing arrangement according to claim 1, wherein at least over a portion of a longitudinal region extending in the direction of the axis of the drill bit, the shaft (32) of the cutting tooth (30) is circumferentially surrounded by the shaft receiver (22).
 16. The securing arrangement according to claim 15, wherein the shaft (32) of the cutting tooth (30) includes at least one calibrating receiver (32.1) set back relative to an inner wall of the shaft receiver (22).
 17. The securing arrangement according to claim 1, wherein the shaft (32) of the cutting tooth (30) is tapered at least over a portion of a longitudinal extension in a direction towards a free end and the shaft receiver (22) is tapered at least in a regional manner, and an outside cross-section of the shaft (32) is smaller than an inside cross-section of the shaft receiver (22).
 18. The securing arrangement according to claim 1, wherein the tool head (31) of the cutting tooth (30) includes at least one radial (38.1) near a region directed radially inwards.
 19. The securing arrangement according to claim 1, wherein the tool head (31) is closed at circumferential end regions with triangular convexly curved shaped faces (36).
 20. The securing arrangement according to claim 1, wherein the tool head (31) has at least one element (39.3) of hard material near a second region directed radially outwards.
 21. The securing arrangement according to claim 20, the at least one hard material element (39.3) is admitted into a web (37.2) disposed near the cutting tooth (30) lying radially outwards and extending in the direction of the axis of the drill bit and protruding above a base part (39) of the cutting tooth (30), and the hard material elements (39.3) protrude in a regional manner radially above the web (39.2).
 22. The securing arrangement according to claim 1, wherein remote from the shaft (32) the tool head (31) of the cutting tooth (30) has a top face (31.1) into which a hard material insert is inserted. 